Gentleman's Agreement is a 1947 movie starring Gregory Peck. He plays a reporter who decides to pretend to be Jewish in order to write an expose on anti-semitism. It shows the impact on his professional and personal life as he begins to realize the extent of the prejudice.
I'm sure it was a big deal in 1947, but I didn't think it held up. The characters were pretty good, but there just wasn't much depth or enough tension.